1. Field of the Invention
This invention relates to a linear motion guide unit applied to various kinds of robots, a semiconductor manufacturing apparatus and cutting and grinding machines, and more particularly to a linear motion guide unit provided with lubricating plates which can be incorporated simply in an existing linear motion guide unit.
2. Description of the Prior Art
In recent years, the mechatronic techniques have remarkably been developed, and a linear motion guide unit has been demanded to improve accuracy and speed and the reduction of dimensions. Moreover, a wider use of the linear motion guide unit has been seen at present with the development of the relative techniques. The linear motion guide unit is used in the technical field of a semiconductor manufacturing apparatus, an inspection machine and an industrial robot. For example, an assembling robot demands the wider use thereof, and from large-sized to small-sized assembling robots are being manufactured. Especially, the linear motion guide unit incorporated in these assembling robots has come to meet the requirements for improving the accuracy and speed and reducing the dimensions, and providing self-lubrication.
A linear motion rolling guide unit shown in FIG. 20 is known. The linear motion rolling guide unit has a slider 1 mounted in a saddled state on a track rail 2 and slid freely thereon via rolling elements circulated along raceway grooves in the track rail 2. The track rail 2 is provided with the raceway grooves 4 in both of longitudinal side surfaces thereof. The track rail 2 is provided with a plurality of mutually spaced fixing holes 13 in a longitudinally extending upper surface thereof. The track rail 2 is fixed on a mounting base 20, such as a bed, a machine base and a working base. In the fixing holes 13 made in the track rail 2, bolts are inserted, which are then driven into threaded holes formed in the mounting base 20, whereby the track rail 2 is fixed on the mounting base 20. The slider 1 has a casing 5 movable relatively to the track rail 2, and end caps 6 fixed to both ends of the casing 5.
The casing 5 is provided in an upper portion thereof with fixing holes 19 used to fix some other machine, a part of a machine, a chuck or a clamp to the casing 5. The casing 5 and end caps 6 are provided in lower surfaces thereof with recesses 10 so that the casing 5 and end caps 6 are saddled at these recesses on the track rail 2 and moved thereon, and the portions of opposite surfaces of the recesses 10 which are opposed to the raceway grooves 4 in the track rail 2 raceway grooves 9. The rolling elements 7, such as balls are inserted in raceways formed by the opposed raceway grooves 4, 9, in such a manner that the rolling elements 7 roll therein. In order to prevent the rolling elements 7 from falling from the casing 5, retainer bands 18 are fixed to the casing 5 so as to enclose a large number of rolling elements 7. Lower seals 8 are provided on lower surface of the slider so as to attain the sealing of clearances between the track rail 2 and slider 1.
The end caps 6 are provided at both sides thereof with claws, by which the rolling elements 7 are scooped from the raceway grooves 4 forming load raceways between the end caps and track rail 2, and direction changing passages for changing the direction of the rolling elements 7 for the circulation thereof. End seals 17 for attaining the sealing clearances between both of longitudinal end portions of the track rail 2 and slider 1 are attached to the end caps 6. The end caps 6 are fixed to both end surfaces of the casing 5 by screws 25 inserted through a plurality of fixing holes. The rolling elements 7 in load regions which roll in the raceway grooves in the track rail 2 are guided into the direction changing passages formed in the end caps 6, and then moved into return passages 12 formed in parallel with the raceway grooves 9 in upper portions of the casing 5, whereby the rolling elements 7 roll in endless circulating passages. Owing to the rolling of the loaded rolling elements 7 rolling in the raceways formed between the raceway grooves 9 in the slider 1 and those 4 in the track rail 2, the track rail 2 and slider 1 can be moved relatively to each other.
The conventional seal means for linear guides include, for example, seal means disclosed in Japanese Patent Laid-Open Nos. 346919/1994, 35146/1995, 200362/1996, 247144/1996 and 247145/1996.
For example, the seal means for linear guides disclosed in Japanese Patent Laid-Open No. 346919/1994 comprise seal means, such as side seals and underseals provided on a slider of a linear guide which have seal lips formed out of lubricant-containing rubber or synthetic resin, and the seal lips contact outer surfaces of a guide rail and seal clearances between a slider and the guide rail, a lubricating oil which oozes constantly and continuously from a lubricant-containing seal bodies being supplied to the parts to be sealed.
A method of manufacturing communicating porous sintered bodies disclosed in Japanese Patent Laid-Open No. 283634/1986 is known as a porous sintered body manufacturing method. The communicating porous sintered body manufacturing method mentioned above is a method of obtaining porous sintered bodies having communicating pores of an average pore diameter of 10-150 .mu.m and an average porosity of 25-45 vol. % by mixing polyethylene powder of superhigh molecular weight and powder of a polyolefin resin molding material with each other at a predetermined ratio, and then sintering the resultant mixture.
In the linear motion rolling guide unit shown in FIG. 20, grease or a lubricating oil is used widely in general as a lubricant. When the lubricant comprises grease, it is supplied from grease nipples 11 to rolling passages of the rolling elements to lubricate the rolling passages. When the lubricant comprises a lubricating oil, the lubricating operation is carried out through pipe joints provided instead of the grease nipples. The linear motion guide unit is provided on end surfaces thereof with end seals usually, so as to prevent waste and dust from entering the slider. The end seals comprises rubber members formed out of nitrile butadiene rubber (NBR), and metal cores.
In recent years, in which the range of use of a linear motion guide unit has been expanded, it has been demanded that imperfect lubrication does not occur even in the condition in which the oil feeding cannot be carried out or under severe condition of use of the guide unit, for example, in an environment in which a large quantity of waste, dust and chips occur and are deposited on parts or in a region of severe temperature conditions. For example, the end seals in the seal means for the linear guide disclosed in the above-mentioned Japanese Patent Laid-Open No. 346919/1994 are formed out of lubricant-containing rubber or synthetic resin, and those in the seal means for the lubricant-containing polymer-lubricated linear guide unit disclosed in the above-mentioned Japanese Patent Laid-Open No. 200362/1996 comprise lubricant-containing polymer members.
In the seal means disclosed in the above-mentioned Japanese Patent Laid-Open Nos. 346919/1994 and 200362/1996, the lubricant-containing polymer members comprise a material obtained by mixing polyolefin polymer and .alpha.-olefin oil with each other, thermally melting the mixture thus obtained, injecting the molten mixture into a predetermined mold, and molding the mixture by cooling and solidifying the same while pressing the same. Thus, complicated, high-degree techniques are required to manufacture the lubricant-containing polymer members.